1. Field of the Invention
This invention relates to liquid meters, and in particular, to the means whereby the motion of the flow responsive element is transferred from the moving element to the register.
2. Description of the Prior Art
Liquid meters of the type with which the instant invention is particularly concerned are known as oscillating piston meters, a typical example of which are show in U.S. Pat. Nos. 2,449,974 dated Sept. 28, 1948, and 4,391,139 dated July 5, 1983. As particularly shown in the latter patent, the meter is generally comprised of a casing which encloses a measuring chamber which in turn contains an oscillating piston as the flow responsive element. A register is also provided exterior to the measuring chamber. Means must therefore be provided to transmit the motion of the oscillating piston to the exterior of the measuring chamber so that the motion may be fed into the register to show the volume of liquid which has flowed through the meter. A conventional method of transmitting the motion of the oscillating piston to the exterior of the measuring chamber is to provide a drive post extending from the piston which engages a drive dog which in turn is mounted for rotation within the measuring chamber on one end of a shaft which is journaled for rotation in the top wall of the measuring chamber. The other end of the shaft protrudes exteriorly of the measuring chamber and carries means to drive couple it to the register mechanism. It has been found, however, that a problem arises with the use of the post-dog drive arrangement of such prior art devices. As the piston oscillates under the influence of liquid flowing through the meter, the velocity of the piston is not uniform throughout its cycle of oscillation. In other words, the instantaneous velocity of a point on the piston will vary depending on what point in the cycle of oscillation the piston is at. This nonuniformity of velocity of the piston causes the post and dog to repeatedly disengage and re-engage as the piston oscillates. Each time the post re-engages the dog, it does so with an impact, the energy of impact being dissipated over a relatively small area because of the essentially line contact between the cylindrically shaped post and the planar contact surface of the dog. These repeated impacts produce a high level of noise which emanates from the meter. This noise is particularly loud and noticable when the meter parts are made from plastic and in such meters, the level of noise may be objectionable, particularly when water meters are installed in residences.